Inhibition in seed germination of Oryza sativa (paddy) by two weed species.

The inhibitory effects of Paspalum scrobiculatum and Echinochloa colonum [E. colona] on rice seed germination were studied. Rice seeds were placed in Petri dishes lined with three layers of filter paper moistened with aqueous leachates (1: 0, 1: 5, 1: 10, 1:25, 1:50, 1: 100, 1:250 and 1:500 dilutions) from leaves, stems, roots and seeds of both weeds. The percentage of reduction in germination was 39.6, 36.0, and 5.0% with leaf, stem, root and seed extracts of P. scrobiculatum and 60.0, 36.0, 7.0 and 20.0 with leaf, stem, root and seed extracts of E. colonum [dilutions used not specified]. These results indicate the allelopathic effects of both weeds on rice seed germination.